Touch screen displays are used in a variety of applications, including informational kiosks, trade show displays, and customer self-service terminals. FIG. 1 is a diagrammatic illustration of a touch screen display system according to the prior art. System 100 includes display screen 102, emitters 104 in emitter arrays 106, 108, and detectors 110 in detector arrays 112, 114. Each emitter 104 in emitter arrays 106, 108 emits light over the surface of display screen 102 that is detected by opposing detectors 110 in detector arrays 112, 114.
When an input device (see 200 in FIG. 2), such as a digit or stylus, touches site 116 on display screen 102, light beams 118, 120, 122, 124 are obstructed and not received by their respective detectors 110 in detector arrays 112, 114. The location of each detector 110 in detector arrays 112, 114 that did not receive obstructed light beams 118, 120, 122, 124 is used to determine the location of site 116 on display screen 102.
The resolution of touch screen display system 100 is proportional to the number of emitters 104 in emitter arrays 106, 108 and the number of detectors 110 in detector arrays 112, 114. A high-resolution touch screen display system uses more emitters and detectors than a low-resolution system. The additional emitters and detectors allow the high-resolution system to determine the location of a selected site (e.g. site 116) more finely and accurately. But both the cost and size of a touch screen display system increase as the number of emitters and detectors in the system grow.